Patt Morrison for July 5, 2011

Genetics vs. environment: the cause of autism is again up for debate with a new series of studies

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Eight year-old Michael Dedrick-Dwyer, who has Cerebral Palsy and Autism, takes 30-minute ride on a horse with therapist Rebecca Reubens and volunteer Kimberly Schuman.

It’s a decades-old mystery that, at times, has turned into a contentious debate: what are the causes of autism and why have the cases of autistic children skyrocketed within the past 30 years? The debate over the causes of autism has centered on whether genetic or environmental factors play the bigger roles, and opinions have shifted as the research has evolved. Genetic factors have been the focus of research for the past 15 years but yesterday the shift was on again, back toward the possibility of environmental conditions playing into the development of autism, from chemicals to medications. A study published yesterday in the Archives of General Psychiatry looked at 192 pairs of twins in California and, using a mathematical model, found that genetics account for about 38% of the risk of autism and environmental factors account for about 62%.

Could prenatal conditions for fetuses, from the area in which mothers live to the kinds of prescription drugs they have taken over their lifetime, play an even bigger role than genetics in predicting autism? Another study, also published yesterday in the Archives of General Psychiatry, looked at the use of antidepressants in mothers, both before and during pregnancy, and the possible connection to autism. A two-fold increase in the risk of autism was found when mothers took antidepressants at some point in the year before giving birth. Is it the environment, your genetics or some combination of both that leads to autism in children, and will we ever have a definitive answer?

Guests:

Joachim Hallmayer, associate professor of psychiatry & behavioral science at the Stanford University School of Medicine; lead author of the autism study on identical twins

Lisa Croen, senior research scientist & director of the Autism Research Program at Kaiser Permanente; lead author of the study on the possible link between antidepressant use in mothers & autism in children


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